Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$144.42	12.631%	$162.6617	$162.66	$162.65	$162.70
Purchase #2	$165.33	4.529%	$172.8178	$172.82	$172.80	$172.80
Purchase #3	$6.96	6.494%	$7.412	$7.41	$7.40	$7.40
Purchase #4	$123.89	3.275%	$127.9474	$127.95	$127.95	$127.90
Purchase #5	$37.75	8.521%	$40.9667	$40.97	$40.95	$41.00
Purchase #6	$33.77	5.444%	$35.6084	$35.61	$35.60	$35.60
Purchase #7	$49.44	11.402%	$55.0771	$55.08	$55.10	$55.10
7 purchase totals =	$561.56		$602.4911	$602.50	$602.45	$602.50